Our model utilizes dielectric functions due to surface parallel excitations only, as the effective dielectric function is derived in a specular reflection geometry. This is a reasonable approximation as out-of-plane excitations are minimal in graphene at energies less than \(\approx 10\,\) eV, and extreme UV radiation is outside of the regime of interest for this study. [1]} A lattice constant of \(2.46\,\) Å is used for graphene, and \(2.50\,\) Å for hBN, as hBN is nearly isomorphic to the graphene, except for the slightly larger lattice constant. [2]}
